Patent GB-989093-A (GB)
Title: Improvements in or relating to the control of clutches or brakes
Inventor: HENDERSON CYRIL
IPC: F16D43/24
Filed: 1960-06-27
Abstract: 989,093. Clutch control: brake regulating devices; fluid pressure control of brakes. S. SMITH & SONS (ENGLAND) Ltd. June 23, 1961 [June 27, 1960], No. 22522/60. Headings F2D, F2E, F2F and F2L. [Also in Divisions G3 and H2] The engagement of a clutch or brake is controlled in response to the deceleration and speed of the input member of the clutch or brake so as to prevent the deceleration from exceeding a limiting value which varies in accordance with the speed. A flywheel 1 is freely mounted on the end of a vehicle-engine crank-shaft 2, an arm 3 being rigidly fixed to the shaft. When flywheel 1 rotates, weight 10 tends to fly outwards increasing the tension in spring 11, and if the crank-shaft decelerates, parts 4, 6 remain in engagement as long as the inertia does not overcome the spring. If the deceleration becomes excessive the flywheel tends to overrun the crankshaft so that parts 4, 6 separate to de-energize a clutch-coil. The deceleration of the input member of the clutch and the engine is immediately reduced so that the switch is re-closed. The average current in the clutch-coil automatically attains a value such that the deceleration does not exceed a limiting value which varies only in accordance with the speed of the flywheel. The switch 5 may be replaced by a resistor. In another arrangement, the initial tension of the spring is varied in accordance with the throttle opening of a power unit which drives the clutch, the throttle opening being indicative of the speed of the input member, Figs. 3, 4 (not shown). In a further embodiment, the clutch is hydraulically operated under the control of a normally-open valve which is closed when the inertia member is displaced from its datum position, Figs. 5, 6 (not shown). The embodiments described may be adapted to control the operation of brakes in an epicyclic transmission system for the drive from a vehicle engine to its road-wheels, the member which is braked constituting the input member of the device. In Fig. 7, an A.C. generator 1 is driven at engine speed, a magnetic particle clutch 45 having winding 47 and transmitting the drive from the engine. A switch 46 is closed to energize relay 11 when the vehicle is starting from rest. Assuming that the switch 46 is open, the voltage at the base of transistor 26 depends upon a positive speed signal and a negative deceleration signal applied through a differentiating circuit. If the deceleration signal becomes excessive, the transistor 26 conducts whereby transistor 31 is rendered conductive and transistors 39, 41, are cut off. Consequently, the current through winding 47 falls to zero, whereupon the deceleration is decreased and the clutch re-energized. When the relay 11 is energized at starting and the speed of the generator 1 exceeds a predetermined value, the base of transistor 26 is driven positive for a short period during each half cycle of the output of the generator, transistor 31 being cut off during each half cycle for a fixed interval dependant upon the rate of discharge of capacitor 30 through resistors 28, 36 and 37. When transistor 31 is cut off an energizing current flows through clutch coil 47. Thus, at low speeds of generator 1, the clutch is completely de-energized, and, at higher speeds, the average clutch energizing current is proportional to the A.C. signal from the generator, and therefore its speed. Specification 649,553 is referred to.